Carburetor



y 1955 R. c. LA FORCE CARBURETOR 3 Sheets-Sheet 1 Filed 001;. 11, 1962 INVENTOR.

ROBERT C. LAFORCE wwwk ATTORNEY May 11, 1965 R. c. LA FORCE CARBURETOR 3 Sheets-Sheet 2 Filed Oct. 11, 1962 A TTORNE Y y 1965 R. c. LA FORCE 3,182,976

CARBURETOR Filed 001;. 11, 1962 3 Sh t s 3 as M I 32 q 36 '18 a2 76 we I: 94 i u z A;

l: 9a 73 84 I00 l2 4 74 90 l MINI Q so a HI I I 2 Z m INVENTOR.-. FIG 4 ROBERT c. LAFORCE A TTORNEY United States Patent C) 3,182,376 CARBURETOR Robert C. La Force, 854 7th St., Beaver, Pa. Filed Oct. 11, 1962, Ser. No. 229,912 3 Claims. (Cl. 261-63) This invention relates generally to carburetors for internal combustion engines and more particularly to improvements in the fuel-air ratio control system thereof.

Carburetor builders have, for years, struggled to accomplish the best balance of fuel to air in order to produce the best economy as Well as the maximum obtainable po-wer. Many attempts have been made to overcome the enrichening tendencies of the venturi tube and fuel jet at the higher velocities. Industry has tried various methods such as fuel metering rods and air bled fuel jets with some degree of success.

Individual inventors seem to lean toward supplying auxiliary air to the manifold usually below the butterfly or throttle valve. The supply of such auxiliary air can be very deceptive inasmuch as an improvement in one area of operation is generally followed by equal and opposite defliciencies in other areas.

In the light of the present invention which shows substantial improvement over the systems previously mentioned, it is intended to show hereafter why previous systems have not provided the correct solution and to disclose how by novel means properly applied, the instant invention overcomes the carburetion problem.

In the first place, the concept of measuring off or metering fuel to accommodate the air flow is extremely difiicult. This is due to the fact that at a 15 to 1 air fuel ratio (by weight) translated into the same ratio by volume, in the manner by which the carburetor must deal with it, we have 8,557.5 to 1 (taking air at C. and 29.92 inches of mercury). By volume then, the fuel is an extremely small part of the aggregate requiring microscopic variations in flow to maintain a balance. Because the fuel is by volume. such a small part of the whole any slight error in calibration renders the Whole charge out of balance.

It is therefore advisable to reverse the process and establish a fuel flow whether constant or variable and then, by means such as shown hereinafter, control the air supply to suit the fuel flow. By this method and structure even fairly large errors in air supply will maintain close to optimum air fuel ratios. i

This cannot be accomplished however by the simple expedient of adding air into the circuit from an already balanced carburetor. This leaves only fringe benefits available in the too rich areas and requires again very precise additions of air from mechanisms which must be too heavily loaded against wide variations in manifold vacuum to remain sensitive to the demand when manifold vacuum is low.

It is for this reason that the automatic balancing air control must be located within or made to communicate with the carburetor itself as between the high speed venturis and throttle valve and that it be made to contribute air to the carburetor throat throughout the range of operaion so that it will be poised against carburetor throat depression only and thus remain constantly sensitive to pressure variations within the throat where rich and lean conditions normally develop.

It is therefore the primary object of this invention to provide an automatic system for obtaining the optimum fuelair ratio in a combustible mixture fed to an engine rom a carburetor over the entire operating range of the engine.

Another object of this invention is to provide a vacuum sensing device which will in response to high manifold 3,182,976 Patented May 11, I965 vacuum adjust an air valve control spring lean for improved cruising economy.

Another object of this invention is to provide spring means of adjusting an air valve spring richer when little or no manifold vacuum is present for improved power and performance.

A further object of this invention is to provide an instantly responsive means of enriching the carbureted mixture so that generally leaner mixtures may be utilized without developing fiat spots on demand for power.

Another object of the present invention is to provide a means "of cutting out the high speed fuel feed earlier than usual up'on deceleration for an improved belnding of the high and low speed systems.

A further object of this invention isto provide an improved method of obtaining the optimum fuel-air ratio in a carburetor connected to feed fuel mixtures to an engine over the entire operating range of the engine.

These and further objects and advantages of the invention will be more apparent upon reference to the following specifications, claims and appended drawings wherein:

FIGURE 1 is a side elevation of the instant invention afiixed to the air chute of a carburetor shown in phantom;

FIGURE '2 is a plan view, partly cut away, showing the inner workings 'of spring control and diaphragm unit of the invention;

FIGURE 3 is a vertical cross section taken along lines 3-3 of FIGURE 2;

FIGURE 4 is a vertical cross section taken along lines 4-4 of FIGURE 2, and

FIGURE 5 is a section view taken along the line 5-5 of FIGURE 3.

Referring to the drawings, FIGURE 1 illustrates an air horn in incorporating a flap valve 12 aflixed to cross spindle 14 which is ofiset from center of air horn 16. Air horn 10 is mounted by flange bolts not shown to air chute 16 and communicates therewith and therethrough to carburetor 18 at the throat 20 between drastically re duced venturi'inserts 22 and throttle valve 24. This makes for an offset flap valve responsive to pressure differential between atmosphere and carburetor throat depression.

Minor adjustments at throttle valve 24- aremade to make the low speed system diminish its output sooner as the throttle is opened. Restricted venturi 22 would normally cause the high speed system to cut in -too early and the increased velocities at 22 would enrichen the mixture excessively and would finally restrict the in- 12 however it may be seen that these adverse conditions are easily avoided. With proper spring control of offset fiap valve 12 it will yield to the depression in throat 20, open and supply air via 26 and 28- to carburetor throat 20. This has the efiect of controlling the beginning velocity at venturi 22 so that it will begin to feed fuel at the optimum time and by further yielding to depressions at 20 as the throttle 24 is opened, flap valve 12 provides the means of preventing excess velocities from occurring at 22 and further of supplying the extra air normally demanded of venturi 22 or of any normal venturi. It it a well known fact that the reason most venturis go over-rich as the velocities increase is that for every doubling of velocity, which means double the supply of air, there is a corresponding increase of fuel flow at 30 equal to 2- /2 times the previous flow. This variation in the flow characteristics of fuel to air normally causes an over rich condition to occur as the velocity through a venturi is increased; Flap valve 12 therefore plays a dual role in overcoming such enrichening tendencies, first, it prevents the velocity from increasing so rapidly at 22 on demand of the engine, and second, since velocity rate increases at 22 will still prevail, though to a lesser degree and since the variation in flow characteristics will still prevail, flap valve 12 will supply the extra air to the mixture and such supply will compensate for the excess fuel normally inherent with increased velocity in a venturi system.

FIGURE 3 shows one preferred embodiment of the flap valve 12 and spring control wherein crank 32 is afiixed by suitable means to spindle 14 extending behind the crank and being connected with spiral, or band spring 34 at 36 by suitable means. Spring 34 is contained within spring housing 38 and is normally made integral with spring housing 38 by means of bent center section 40 fitting slot in lug 42 which is affixed permanently to housing 38 and extends inwardly toward spiral spring. Spring housing 38 is secured in a rotatably adjustable fashion upon cast boss 44 of air horn by means of screws 46 and body clamps 48. From this description it can be seen that by loosening screws 46, it is possible to rotate spring housing 38 and restraining lug 42 and thereby adjust the tension of spring 34 upon crank 32 spindle 14 and flap valve 12. After adjusting, counterclockwise for more tension, or clockwise for less tension the locking screws 46 are re-tightened, and the spring tension remains as adjusted through all phases of engine load and speed as far as this adjustment mechanism is concerned.

The instant invention deals with a new and novel automatically adjustable means of controlling this spring tension. In FIGURE 1 an angle bracket 50 i attached to spring housing 38 by means of cap screws 52 and supporting vacuum diaphragm unit 54 (of conventional design) by way of mounting screws 56. On the end of vacuum responsive plunger 58 there is mounted an adapter plate 60 by way of screw 62. The several holes in adapter 60 provides a choice of locations for swivel 64 better seen in FIGURE 2. Swivel 64 is mounted in the top hole and secured free to rotate by way of washer 68 and pin 70. In the instant invention spring retaining hub 42 has been extended through spring housing 38 and is secured free to rotate by shoulder 72 and retaining lock washer 74 which is secured to hub extension 76 by set screw 78.

Spring retaining shaft 76 carries an adjustable crank arm 80 which is secured to shaft 76 by set screw 82. At the extreme end of shaft 76 there is an adjusting knob 84 secured to shaft 76 by set screw 86. Crank arm 80 has a plurality of connecting link holes 88. The final connecting link 90 is a bent rod with the short bend in the uppermost hole 88 of crank arm 80 and the long arm adjustably secured to swivel 64 by means of cross hole 92 and lock screw 66;

In viewing FIGURE 1 it may be seen that by moving connecting link 90 outwardly along crank 80 to any of the holes 88 provided therefore a variation of moment arms are obtainable and the angular travel of crank 80 may be shortened. By looking at FIGURE 2 it may be seen that the angular travel of crank 80 greatly atfects the retaining position of hub 42 and thus the tension of spiral spring 34 acting upon crank 32 and therethrough to spindle 14 and valve 12.

FIGURE 2 shows an adjustable stop arm 94 secured to the extreme opposite end of paddle shaft 14 by means of set screw 96. Arm 94 is a 2 bar extending down to air chute 16 and carries at the lower end adjusting screw 98 and lock nut 100. This adjusting screw 98 is provided as a means of presetting the minimum closed position of valve 14. The action of this stop may be better seen by viewing FIGURE 4.

In FIGURE 2 it may be seen that diaphragm housing 54 contains the conventional diaphragm 102 and compression spring 104 acting within vacuum chamber 106 to move plunger 58 to the right in its most extended position. Vacuum line 108 communicates with the intake manifold and is secured to diaphragm unit 54 by way of fitting 110.- In this way the intake manifold vacuum is made to communicate with vacuum chamber 106 in opposition to spring 104 and tends to pull vacuum plunger 58 to the left.

In viewing FIGURE 1 it can be seen that the vacuum acting on plunger 58 will cause the plunger to move to the left and by means of connecting link will rotate crank arm 80 and shaft 76 and spring retaining hub 42 clockwise. Viewing FIGURE 2 this tends to unwind spiral spring 34 and relieves some of its tension acting upon crank 32 and valve spindle 14 thereby allowing valve 12 to yield to carburetor throat depression and admit air through chute 28 to lean out the air fuel mixture. It should be obvious from this explanation that when the manifold pressure is raised, as by opening the throttle valve, the diaphragm spring 104 acting in opposition to manifold vacuum will reverse the direction of plunger 58, move it to the right and by way of connecting linkage previously described wind spring 34 tighter increasing its tension on crank 32 and shaft 14, thus urging flap 12 toward the closed position. This tends to resist the carburetor throat depression by closing down on the flow of air through chute 28 and thereby increasing the flow of air and fuel through venturi 22 which enrichens the resultant mixture for power.

This vacuum operated spring adjusting means provides for a richer mixture during acceleration, for a leaner mixture during deceleration and for intermediate mixtures responsive to vacuum conditions in the intake manifold.

The initial spring setting may be adjusted by simply loosening set screw 82 on crank 80 while holding adjusting knob 84; then by turning adjusting knob clockwise for leaner settings or counterclockwise for richer settings and relocking set screw 82. This may be done with the engine otf or on, and by indexing knob 84 or retaining knob 74, a record of the settings may be recorded or used for tune-up data.

Stop 98 is set with the engine running by opening the throttle 24 from idle position using the throttle adjusting screw not shown until mixture starts to go too rich or too lean by analyzer analysis. If the mixture goes too lean, stop screw 98 is turned counterclockwise allowing flap valve 12 to go toward closed until the mixture returns to normal and locknut is then relocked. If the mixture goes too rich, the above procedure is reversed until the mixture returns to normal and then locknut 100 is relocked. By this procedure a perfect transference from the low speed feed system to the high speed venturi feed system is obtainable, taking into account any errors of manufacture or float setting or carburetor condition which otherwise interfere with correct balance.

The instant invention has another notable improvement over conventional systems while the engine is decelerating. Normally, without the vacuum controlled spring 34 or on standard carburetors with fixed venturis, if the velocity in the venturis is fixed correctly to start fuel flow While accelerating, then after the fuel has begun to flow and has overcome surface tension and inertia, upon deceleration, the fuel continues to flow at air velocities through the venturis which are lower than it took to start the fuel. Therefore, the mixture goes over rich during deceleration. This does not happen with the vacuum controlled spring 34 in operation. Upon deceleration the vacuum control adjusts spring 34 leaner allowing paddle 12 to yield to the carburetor throat depression, thus supplying air flow past paddle valve 12 which supply of air reduces the velocity of air at the vena contracta 30, and the flow of fuel therefrom is interrupted early enough to prevent the mixture from going over rich.

No flat spots are apparent from the above system going from very lean cruising mixtures to wide open throttle or in slowly urging the throttle open due to the agility of the vacuum control apparatus in response to the sensing and harnessing of manifold vacuum to reset the air control spring 34 upon demand for power.

In FIGURE 1 a pull spring 112 is shown connected at one end to stationary bracket 54! and at the other end to crank arm 80 urging the crank 80 toward a leaner position. By viewing FIGURE 2 it may be seen that such a spring is counterpoised against diaphragm spring 104. The purpose of this spring is to provide a cruising range of between 20 inches of mercury and 15 inches of mercury in which diaphragm spring 1634 cannot act to enrich the mixture. Viewing FIGURE 2, it may be seen that pull spring 112 can be calibrated so that 15 inches of mercury or above within vacuum area 106 acting on diaphragm 102 plus the tension of spring 112 on arm 30 will hold plunger 58 retracted to the extreme left, thus holding the mixture lean between 15 and 20 inches of mercury. It may also be seen that if the vacuum drops below 15, to say 14 inches, then diaphragm spring 104 may act at such lower vacuum and against the pull spring 112 to move the diaphragm plunger 58 to the right and enrich the mixture.

In summary therefore, it should be apparent to one skilled in the art that the invention provides a structure and method for automatically obtaining and maintaining an optimum fuel-air ratio in a carburetor overthe entire operating range of a given engine by means responsive to engine power demand. In brief, the carburetor is provided with a secondary air passage or chute 16 in which a biased flap valve 12 is positioned. The flap valve is carburetor throat pressure drop responsive to move toward a more open condition against the bias of a band spring 34 acting on the mounting spindle 14 for valve 12. Intake manifold pressure variation responsive means including unit 54 acts through a suitable linkage to vary the opposition of the spring to opening of the valve 12 by pressure drops in the carburetor throat. Since the adjustrnent of the spring is in accord with engine power demand and since the reaction created in the linkage is practically instantaneous in effect, then the fuel-air ratio will be maintained at an optimum in accord with the control effected on flap valve 12.

The applicant realizes that the actual structure may be subject to many detail variations well within the purview of this inventor, all of which are intended to be included in a liberal interpretation of the appended claims.

What is claimed is:

1. A carburetor for an internal combustion engine including an intake manifold and a throttle valve comprising a main air flow passage from the carburetor through the throttle valve to the intake manifold, a combustible mixture generating means positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, a secondary air flow passage connected to the main air flow passage between the mixture generating means and said throttle valve, a flap valve carried by an offset spindle in said secondary air fiow passage, said spindle having a portion projecting exteriorly of the passage, said flap valve being responsive to the pressure variations created in the main air passage in the area of the connection between the main and secondary air passages to move in an opening direction during engine operation, biasing means carried by the carburetor and connected with the projecting portion of the valve spindle to oppose the opening of said valve means, and intake manifold pressure responsive means comprising a spring loaded diaphragm interconnected by a linkage and crank arm connected to the biasing means to vary the action of said biasing means in accord with engine power demand.

2. The invention according to claim 1 wherein the biasing means comprises a spring, the tension of which is adjusted through the connection with the linkage and crank arm.

3. The invention according to claim 1 wherein a spring of preselected tension is connected with the crank arm to oppose the spring action of the spring loaded diaphragm to establish under preselected pressure conditions a dormant condition for said manifold responsive means representative of a cruising condition of the engine.

References Cited by the Examiner UNITED STATES PATENTS 1,956,657 5/34 Scheel.

2,124,492 7/38 Marshall 123-124 2,207,152 7/40 Huber 261--63 2,680,605 6/54 Bracke 261-63 2,877,998 3/59 Cornelius 12397 X 2,944,646 7/60 Willrner 12397 X 2,998,233 8/61 Marsee. V

GEORGE D. MITCHELL, Primary Examiner.

HERBERT L. MARTIN, Examiner. 

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE INCLUDING AN INTAKE MANIFOLD AND A THROTTLE VALVE COMPRISING A MAIN AIR FLOW PASSAGE FROM THE CARBURETOR THROUGH THE THROTTLE VALVE TO THE INTAKE MANIFOLD, A COMBUSTIBLE MIXTURE GENERATING MEANS POSITIONED IN SAID MAIN AIR PASSAGE ON THE OPPOSITE SIDE OF THE THROTTLE VALVE FROM SAID INTAKE MANIFOLD, A SECONDARY AIR FLOW PASSAGE CONNECTED TO THE MAIN AIR FLOW PASSAGE BETWEEN THE MIXTURE GENERATING MEANS AND SAID THROTTLE VALVE, A FLAP VALVE CARRIED BY AN OFFSET SPINDLE IN SAID SECONDARY AIR FLOW PASSAGE, SAID SPINDLE HAVING A PORTION PROJECTING EXTERIORLY OF THE PASSAGE, SAID FLAP VALVE BEING RESPONSIVE TO THE PRESSURE VARIATIONS CREATED IN THE MAIN AIR PASSAGE IN THE AREA OF THE CONNECTION BETWEEN THE MAIN AND SECONDARY AIR PASSAGES TO MOVE IN AN OPENING DIRECTION DURING ENGINE OPERATION, BIASING MEANS CARRIED BY THE CARBURETOR AND CONNECTED WITH THE PROJECTING PORTION OF THE VALVE SPINDLE TO OPPOSE THE OPENING OF SAID VALVE MEANS, AND INTAKE MANIFOLD PRESSURE RESPONSIVE MEANS COMPRISING A SPRING LOADED DIAPHRAGM INTERCONNECTED BY A LINKAGE AND CRANK ARM CONNECTED TO THE BIASING MEANS TO VARY THE ACTION OF SAID BIASING MEANS IN ACCORD WITH ENGINE POWER DEMAND. 